This application describes neuroanatomical studies designed to re- examine the organization of the cortical projection to subcompartments in the "limbic" and non-limbic striatum of the rat. The "limbic" sector receives voluminous and partly overlapping inputs from the cortex as well as structures of the limbic system suggesting its role as an interface between circuits underlying motor and motivational aspects of behavior. This is further substantiated by the findings that the fundamental dualism in the afferentation of striatum is reflected in its output relationships with the pallidum, thalamus and cortex. The basic hypothesis is that the heterogeneity of striatal function, demonstrated by several behavioral and neurophysiological studies, as regionally distinct subunits is determined by specific cortical afferents and their relationships to other striatal afferents, cellular clusters and neurochemical domains. The organization of the main cortical projection to each of 4 subregions (ventromedial, dorsomedial, ventrolateral and dorsolateral) of the striatum will be studied. The shape, size and location of each longitudinal cortical projection strip will be mapped in stereotaxic coordinates on three-dimensional maps of the striatum by the aid of a computer-aided charting and reconstruction system (specific aim #1). The main purpose of the other experiments is to determine the pattern of overlap or interdigitation of the major cortical projection zone to the distribution of other afferents from the cortex (specific aim #2) to afferents from midbrain dopaminergic system and amygdala (specific aim #3) and to the cellular clusters (specific aim #4) and to neurochemical domains (specific aim #5). The study will consist of a detailed analysis at the light and electron microscopic level using anterograde tracing techniques (the autoradiographic, HRP, and PHAL methods) and immunocytochemistry. The long- term objective is to understand the neuroanatomical basis for the role of the striatum in the integration of movement, mood, and cognition. Knowledge of striatal organization in terms of afferent, cellular and neurochemical compartments should contribute to the identification of neural substrates involved in mental disorders characterized by dysfunctions in kinetic, mood or ideational states.